1. Field of the Invention
This invention relates to an airconditioning system for a vehicle which offers rapid and precise temperature control notwithstanding varying ram air conditions.
2. Disclosure Information
The design of vehicular airconditioning systems and controls has presented a variety of problems to the engineer. Not surprisingly, a variety of solutions to specific problems has resulted. One of the problems which has been addressed is the control of the mass flow through a vehicle in terms of not only the total flow through the vehicle but also the direction of the airconditioned mass flow through the vehicle. U.S. Pat. No. 3,403,855 discloses a system for damping an outside air intake port as a function of vehicle speed. U.S. Pat. No. 3,861,282 discloses a system for controlling blower speed as a function of vehicle speed. Japanese Patent No. 60-78815 discloses a system in which electrical power fed to an airconditioning system blower is reduced when the occupants of the vehicle open a window. None of the systems disclosed in the previously listed patents is capable of controlling the temperature of air processed by the airconditioning system in response to changes in blower speed and power consumption caused by ram air effects.
U.S. Pat. No. 4,759,269, which is assigned to the assignee of the present invention, discloses a system for maintaining independent air flows to two or more separate segments of the interior of a motor vehicle The '269 Patent does not, however, deal with the problem of maintaining constant system temperature or mass flow during changing environmental conditions.
U.K. Patent Application No. 2,093,233 discloses a system and method for regulating the quantity of air supply to the interior of a vehicle in which variations in the current being supplied to the blower motor are used to damp the air inlet to the vehicle at a location upstream of the blower. The system of the U.K. patent application suffers from a serious fault insofar as the system is incapable of compensating for an operating condition wherein the pressure at the air inlet is less than that of still air. Such a condition could be encountered, for example, when a tailwind having a velocity in excess of the linear velocity of the vehicle impinges upon the vehicle. The system of the U.K. application suffers from additional drawbacks. For example, the outside damper assembly causes added system complexity, cost, package space and reliability concerns. Japanese Patent No. 57-4418A discloses a system in which an outer air damper is controlled as a function of detection of a gas within the interior of the vehicle. This system, too, is incapable of correcting for ram air impinging upon the vehicle.
U.S. Pat. Nos. 4,382,463 and 4,482,009 deal with distribution of mass flow within the passenger compartment of the vehicle. Each discloses a system for redistributing mass flow within the passenger compartment based upon the occupancy of the passenger compartment.
U.S. Pat. No. 4,364,513 discloses a system for controlling discharged air based upon the sensing of occupants within the vehicle.
U.S. Pat. No. 4,518,032 discloses a system for controlling the various components of a vehicular airconditioning unit so that the blower speed will be limited while operating in the heating mode so as to prevent excessive heating of the interior compartment of the vehicle.
It is an object of the present invention to provide an airconditioning system having the capability of responding rapidly to changes in the ram air impinging upon an air inlet of the airconditioning system.
It is an advantage of the present airconditioning system that changes in ram air impingement upon the air inlet of the system will be met by adjustment of the blower speed and heat flux of the airconditioning system without the necessity of waiting for the temperature of the interior of the vehicle to change.
It is yet another advantage of the present airconditioning system that comfort of the vehicle's passengers will be maintained without the need for additional flow control doors.
It is a feature of one aspect of the present invention that a control system according to this invention will not need a separate device for measuring the speed of the airconditioning system's blower but will employ a signal generated by the blower motor itself for this purpose.
Other objects, features and advantages of the present invention will become apparent to the reader of this specification.